I think your idea has potential if I am being honest. It kind of sounds like a return to their roots in a way. These places use to be actual gaming boutiques.
that stuff would actually get me to walk into a gamestop.
free RAM/PSU/mobo/whatever testing would be useful on occasion. instead of spending time on a forum, or troubleshooting yourself, just take your parts to get professionally tested. thatd be nice.
used PC parts trade-in? never seen that before anywhere. would be better than sketchy ass craigslist.
old console stuff (repairs, refurbishment, upgrades) may not be the most high-demand or profitable thing... but there's really no good current alternative. ebay/amazon/walmart is rife with counterfeits/misrepresented stuff. and it'd buy them some street cred.
but they'd need to develop a certification training process for their employees, so they actually know what theyre doing. plus everything else i mentioned = higher operating costs.
but, over time... gamestop might actually be seen as.... respectable.
and id actually go. my friends would too.